Philipt,
I'm not a professional painter. I would hand sand the 2k primer dry with 320 and shoot the color. All your bodywork should be finished by now. The 2k seals the substrate and when sanded give a means of adhesion between primer and finish coat.
If you sand through the 2k with a DA or whatever, you are back to square one...bare metal that needs to be addressed. The 2k should be as perfect as the finish coat is, it just needs tooth to allow the finish coat to hook to it.
This is how I see it in my minds eye!
Stuart
